Instrument Prediction of the Lean Content of Pork Carcasses Using Ultrasound or Light Reflectance

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Abstract
The Hennessy and Chong Fat Depth Indicator (FDI) and a compact ultrasonic instrument (Lean Meter) were used to measure backfat thickness in a sample of 152 pork carcasses. Fat thickness readings were taken 5 cm off the dorsal midline at five locations [shoulder (SH), midback (MB), last rib, (LR), loin (LO), lumbar (LU)] on the intact carcass immediately after sticking and exsanguination, and on the left side of the split carcass. Ruler measurements were taken on the dorsal midline at the same five locations on the split carcass. Accuracy for the prediction of carcass retail yield or lean percentage was similar for readings made on the intact or split carcass. Accuracy for the prediction of retail yield from a single fat reading was highest for the FDI reading taken at the MB [residual standard deviation (RSD), 2.15%] and lowest for readings taken at the SH (RSD 2.52%). The Lean Meter and ruler gave similar accuracy for the prediction of retail yield (RSD ≏ 2.38%). The FDI reading taken at the LO provided the most accurate prediction of carcass lean percentage (RSD 3.26%), while the Lean Meter and ruler readings again gave similar, but lower accuracy (RSD ≏ 3.50%). Addition of all five fat readings, carcass weight and loin eye area by stepwise multiple regression only gave small positive increases in the amount of variance explained in either retail yield or lean yield over that provided by a single measure of fat thickness. Lean yield in individual cuts was predicted most accurately in the ham (RSD, 1.37%) both by the FDI and Lean Meter. It was concluded that the FDI was superior to the other measuring techniques and that a single measurement of fat thickness at the MB or LO would suffice for the prediction of retail yield or lean percentage, respectively, in commercial carcass evaluation. Copyright © 1983. American Society of Animal Science. Copyright 1983 by American Society of Animal Science

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